http://soccer-ref.quietfire.com/ussf...F-ATR-1997.pdf
This is the best that I can do for you.
Click on the above link. Scroll down to page 48 and find passage 15.3, the diagram of legal and illegal feet placement is below it.
This is an electronic copy of the ATR from 1998, but this ruling has not changed. The 2005 version is available for purchase only from the USSF.